Digital & print resources available

IRIS offers a variety of resources for the
seismological community and general public
including online interactive materials,
regular newsletters, brochures,
webinars, past event materials. We also offer
digital copies of our proposals and reviews
for download.

Syngine is smart:

Syngine uses IRIS webservices to look up receiver location given network and station name(s) and can accept event IDs (e.g. from GCMT) for origin and moment tensor parameters. Syngine can also window traces based on travel times for any phase.

Syngine is fast:

Since the databases for models are precomputed and running “hot” on IRIS servers (explanation), only Green’s Function extraction, parameter look-ups and basic processing (e.g. resampling, source convolutions) are done. Requests can be fulfilled as fast as fractions of a second, though connection bandwidth, load from other user requests, and complexity of request can add significant time.

Choosing a new sampling rate (dt):

In order to avoid aliasing, downsampling from the database dt is not allowed by Instaseis, only upsampling. If a model has a database dt=0.5, dt=0.1 is allowed, dt=1.0 is not allowed. Detailed examples on resampling

Default source:

By default Instaseis returns the response to a very narrow Gaussian source time function with a full-width at half-max of approximately two-thirds the shortest period resolved, which is as close to a delta function as possible with AxiSEM.

Geodetic/Geocentric Latitudes:

AxiSEM and Instaseis, which drive Syngine, use geocentric latitudes. Station and earthquake coordinates use geodetic/geographic latitudes. It is common practice in seismology to convert from geodetic/geographic to geocentric latitudes in order to calculate distance using spherical geometry. Syngine also does this.

Headers convention for SAC output

When output is chosen as saczip, the SAC files will have header values populated. Header fields of note for Syngine SAC files are:

Tutorials:

Using FetchData and SAC to compare Syngine synthetics & data:
A small amount of post-processing is required if users wish to directly compare data and synthetics for a given earthquake. Synthetic seismograms from Syngine are calculated as displacement for a point-like source. Comparing to data requires correcting for instrument gain, a finite width source (not performed here), and sometimes filtering. The following example uses the 2010-05-24 Western Brazil 582km deep M6.5 event. FetchData is available here.

Downloading model databases:

Users can download the databases for entire models as .netcdf4 files. Within the model directories are PZ and PX folders for the vertical and horizontal databases, respectively, which have the ordered_output.nc4 files needed to run Instaseis locally.